Hi,
I am irradiating some mammalian cells comparing both X-rays and protons. I know what dose I am exposing my cells to using X-rays, for example 4Gy, but if I want to radiate with protons how can I work out the equivalent dose in protons?
Thank you for any guidance
The dose depends on the energy of the protons. The main problem is to determine the stopping power. Please give some more infos.
For protons of low energy (less than 10 MeV) is the biological equivalent of X-ray dose is approximately 10. More specifically it is calculated by calibration of specific apparatus ionization chambers in terms of absorbed dose to water.
If you want to calculate the proton dose you will find an established protocol in IAEA 398. I attend this report for you.
Thank you for you help, I think I will be using 3Mev protons for my irradiation
I´ve done some look out for papers and found two lectures which I append. Because RBE can be different as for different injuries it is very difficult to give you a clear statement. Please read the following papers (one from Havard, the other one from Zurich uni)
In addition to the information supplied by Hanno, see
http://www.nist.gov/pml/data/star/
If you mean a biologically equivalent dose, you just compare the biological effectiveness of X-rays and protons at varying absorbed dose, obtain the relative biological effectiveness (RBE) value, then calculate Gy-Eq (RBE weighted dose).
However, biological effectiveness varies among photons depending on its quality (e.g., mean RBE of 50 kV and 200 kV X-rays relative to 60Co gamma-rays for dicentric chromosome aberrations are 4.0 and 2.5, respectively, https://www.ncbi.nlm.nih.gov/pubmed/16819136 ), so a choice of a reference radiation is important. Also, even with the consistent reference radiation is employed, RBE differs depending on biological endpoints, and increases with decreasing dose, dose per fraction and dose rate to a presumed maximum value.
More specifically, proton RBE differs with dose average LET, increases >1.1 at >2 keV/µm and >1.5 at >10 keV/µm ( https://www.ncbi.nlm.nih.gov/pubmed/28072575 ).
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